1. Field of the Invention
The present invention relates to a chucking device for fastening a tool in a machine tool, particularly in the form of a shrink-fit chuck tool holder for cylindrical, particularly circular cylindrical tools, and to a chucking device for tensioning tools by the shrink-fit chuck.
2. Discussion of the Background
In metal machining operations, today primarily machine tools with high levels of automation are used in production. The chucking and gripping systems, into which the insert tools are clamped and which in turn are held in corresponding holders of the machine tool, for example standardized cylinder shank holders or hollow taper shank (HSK) jaws, significantly influence the quality of workpieces as well as the efficiency of the production processes.
Compared to conventional chucking devices, such as three-jaw chucks or extension chucks, shrink-fit chuck tool holders have greater rigidity in terms of the tool/tool holder unit and achieve greater transmittable torque. As a result, surface improvements on the workpiece, greater manufacturing precision and a longer service life of the tool can be achieved and production processes with extremely high rotational speeds and feed rates can be implemented, for example the so-called high-speed cutting (HSC).
Conventional devices available on the market for chucking insert tools in shrink-fit chucks are provided with a heating unit, for example using hot air or with the help of an induction coil, by which a tool holder is expanded so that the tool (which is still cold) can be inserted in the shank of the tool holder. After cooling and the associated shrinkage of the tool holder, the tool is tightly clamped in place. This way, low pairing tolerances for the pairing of the tool and tool holder and an accordingly tight fit of the tool are achieved.
Clamping devices in this category, particularly shrink-fit chucks, and chucking fixtures, which are also referred to as shrink fixtures, are described, for example, in the documents DE 101 38 107 A1 and EP 830917 B1.
To ensure clean positioning of the cold tool on the shrink-fit chuck, the tool shank is typically provided with a chamfer. To facilitate the insertion process, the recess of the shrink-fit chuck provided for accommodating the tool shank according to EP 830917 B1 has an insertion section, which allows pre-positioning of the tool shank in the cold state of the tool holder.
In this known case, the configuration is selected such that the insertion section holds the tool until the temperature of the shrink section or of the shrink-fit chuck is sufficiently high and the inside recess has expanded so much in terms of width or diameter that it has reached, or even exceeds, the outside dimension of the shank. When the tool and hence the shrink-fit chuck are oriented vertically in the shrink fixture, the tool glides into the shrink-fit chuck under the effects of gravity.